1. Field of the Invention
The present invention relates to improved apparatus for associating an electrical device with a mounting therfor and, more particularly, to improved apparatus for maintaining an electrical device closed in a mounting, for permitting convenient opening of the closed device in the mounting and removal of the opened device therefrom, and for facilitating convenient and easy insertion of the device, and closing of the inserted device, in the mounting.
2. Discussion of the Prior Art
Electrical devices or components, such as power fuses, current-limiting fuses, and blades, may be included in electrical circuits and may be located on a utility pole or on a wall of a vault or room, or may be present in pad-mounted or metal-enclosed electrical gear. The devices are normally held closed and latched in a mounting, in which they may be both moved to affect the continuity of the circuit and to be rendered accessible for inspection, removal or replacement.
A typical device mounting includes first and second spaced brackets which may be affixed by spaced insulators to a utility pole, a wall of a vault or room, or a wall or panel of an enclosure or cabinet. When the device is closed and latched in the mounting, each of the spaced brackets is adjacent to a respective end of the device. One end of the device, usually the lower one, may include or carry a trunnion which is selectively insertable into and removable from a hinge on the first, lower bracket. When the trunnion is in the hinge, the device is rotatable to move the second end of the device toward the second, upper bracket during closing movement of the device and to move the second end of the device away from the second bracket during opening movement of the device. The second end of the device may include or carry an assembly, such as a pull-ring or the like, which is manipulable by a tool such as a "hot stick." The trunnion and the pull-ring may be integral with the device (as is typical with blades) or may be carried by or be integral with fittings permanently or removably mounted to the ends of the device (as is typical with fuses).
The following operations involving the device are typically performed at various times: (1) insertion of the trunnion into the hinge, (2) rotation of the device after such insertion to close and latch the device upon application to the assembly of a pushing force, (3) unlatching and rotation of the device when the trunnion is in the hinge for opening the device upon application to the assembly of a pulling force, and (4) removal of the trunnion from the hinge, after the device is open, for inspection, replacement, or the like. A typical pull-ring (or similar assembly) on the device rather easily permits operations (2) and (3) to be performed with a standard "hot stick." Specifically, a hook or prong on the "hot stick" may be easily engaged with an aperture or "eye" of the pull-ring, following which the pushing or pulling force may be easily applied. However, where the device includes a prior art pull-ring, operations (1) and (4) usually require the use of one or more additional tools, a plurality of different maneuvers with the " hot stick," or both.
Since the hook or prong of a standard "hot stick" cannot grasp the pull-ring or the body of the device (it can only pull or push on the pull-ring), the performance of operation (1) or (4), following the performance of operation (2) or (3), requires the use of an additional tool which can both engage the pull-ring and support the body of the device (for example, a tool such as the GRAPPLER, sold by the assignee hereof), the use of an additional tool such as a clamp which can engage the body of the device, or repositioning of the hook or prong. The use of either of the two additional tools (which normally occurs where the mounting is a so-called 45.degree. opening mounting) permits the device to be lifted and transported, thus permitting the trunnion to be either inserted into or removed from the hinge. Repositioning of the hook or prong is typical with so-called 180.degree. opening mountings. When the device is opened in such a mounting, the trunnion is pivoted 180.degree. from its normal orientation in the hinge, so that the "top" of the device hangs "down." Following opening of the device, the hook or prong is removed from the pull-ring, engaged with an "eye" in the trunnion, and lifted to remove the trunnion from the hinge. Insertion of the trunnion into the hinge and closing of the device are achieved by a reverse, multi-step sequence.
A tool often referred to as a "shotgun stick" is known. This tool, which is typically used to remove or emplace a so-called "elbow," includes a hook-like member which may grasp or clamp a pull-ring or an "eye" on the elbow for removal or emplacement thereof. "Shotgun sticks" have not typically been used to manipulate devices such as blades or fuses for reasons developed below.
In many prior art arrangements, manipulation of the pull-ring is required to unlatch and open the device. This manipulation may comprise engaging the pull-ring with the hook or prong of a "hot stick" and then rotating or pivoting the pull-ring in a vertical plane. Pivoting or rotation of the pull-ring may move a latch lever carried by the upper end of the device to disengage the latch lever from a latch member, such as a protruding lip or other feature, on the second, upper bracket. In some arrangements, pivoting of the pull-ring moves a latch member carried by the upper bracket out of engagement with a lip or other feature on the upper end of the device. In either event, after the upper end of the device is no longer latched and held in the upper bracket and the device is opened, the pull-ring and/or the body of the device are grasped or otherwise supported and the electrical device is lifted upwardly to remove the trunnion from the hinge along the lines described above.
Since the unlatching, opening, and removal of the device can usually be achieved with a "hot stick" alone or by the use of a tool in addition thereto, there is no need to use a "shotgun stick," although such use is theoretically possible. Further, it is also theoretically possible that the grasping performable by a "shotgun stick" might enable the devices of prior art arrangements to be unlatched, opened, and removed therewith, although such is far from common (if it occurs at all). Unlatching manipulation of prior art assemblies requires that a worker rotate or pivot the pull-ring. At times, the relative height of the worker, the tool manipulated thereby (whether a "hot stick" or a "shotgun stick"), and the pull-ring are such that application of a rotative or pivoting force to the pull-ring is inconvenient or quite difficult. Further, if a "shotgun stick" were to be used to unlatch or open the fuse, binding might occur if the "shotgun stick" too firmly grasped the pull-ring as the pull-ring or the device rotates. At least opening rotation of the pull-ring requires that the interior angle between the device and the tool be able to freely increase. The lack of assurance that such binding will not occur (and is easily avoidable when a "hot stick" is used) probably accounts, in part, for "shotgun sticks" not being used to open devices in the past. Further, if the tool is a "shotgun stick" which firmly grasps the pull-ring, binding may be experienced as the device is being opened and the interior angle between the tool and the device tends to increase.
After reinsertion of the trunnion into the hinge (following removal of the device from the mounting), closing rotation of the device causes the interior angle between the tool and the device to decrease. Such a decrease is easily achieved with a "hot stick," the hook or prong of which does not bind in the pull-ring. However, if the tool is a "shotgun stick" or other tool which grasps the pull-ring, the decrease in this interior angle may effect a rotative or pivoting motion of the pull-ring, as well as binding. Rotation of the pull-ring as the device is being closed may result in the pull-ring being sufficiently rotated to prevent latching of the upper end fitting in the upper bracket when the device is supposed to be closed. Whether this last-noted effect occurs or not, the decrease in the interior angle between the tool and device may, again, result in binding if the tool too firmly grasps the pull-ring.
Attempts to insert the trunnion into the hinge may be achieved with the worker holding the tool level with, slightly above, or slightly below the lower bracket. Unless the tool includes facilities for supporting the device, in prior art arrangements, the trunnion is usually not presented at a convenient angle relative to the hinge for easy insertion thereinto, absent clumsy or strenuous manipulation of the tool and the device.
Lastly, in opening or closing the device, the worker may attempt to adjust the tool to a convenient angle of attack for the application of the pulling or pushing force to the tool and the pull-ring. It the tool grasps the pull-ring, this adjustment may pivot or rotate the pull-ring to effect untimely unlatching of the upper end fitting from the upper bracket, or to render the upper end fitting incapable of being latched in the upper bracket when such latching is desired.
One object of the present invention is to provide improved apparatus for associating an electrical device with a mounting therefor which avoids the above described shortcomings. Another object of the present invention is to provide improved apparatus for associating an electrical device with a mounting therefor which contains few parts and is simple and economical to construct.